Vacuum electric tube device



"'1 ROBENSQN VACUUM ELECTRIC TUBE DEVICE 2 Sheet-$heet Filed Nov. 14 1925 INVENTORO Earnesf Y.Robmson ATTORNEY Aug I6, 1-93". E. Y. ROBINSON VACUUM ELECTRIC TUBE Dmitri:

Filed Nov. 14, 1928 2 Sheets-Sheet a 10. 0000 m nb400o b v w s d l INVENTOF? Earnesf Y. Robinson I/ ATTORNEY ture at which it will emit electrons.

Patented Aug. 16, 1932 UNITED STATES PATENT, OFFICE ERNEST YEOMAN ROBINSON, 0F E'NFIELD, ENGLAND, ASSIGNOR TO ASSOCIATED ELEG- TRICAL INDUSTRIES, LIMITED, A COMIANY OF GREAT BRITAIN VACUUM ELECTRIC TUBE DEVICE Application filed November 14, 1928, Serial No. 319,348, and in Great Britain December 18, 1927.

This invention relates to vacuum electric discharge tube devices and more particularly to the anode electrode thereof.

The invention is notably, but not exclusively, applicable to valves having equipotential cathodes adapted to be raised to the electron emitting temperature by means of a heater connected to a high voltage source of supply, such-as ordinary house electric light mains. In such valves, the cathode surface must of necessity be comparatively large and the cathode consequently must dissipate a correspondingly large amount of heat which is confined by a tubular anode and, particularly if the inter-electrode gap is short, may result in the grid being brought to a tempera- T his is especially the case when the cathode is of the oxide coated type.

This restraining of heat radiated from the cathode may be reduced for example by emloying an anode which does not provide a iieat enclosure for the cathode. For instance, the anode may consist of one plane sheet. Such a construction, however, possesses several disadvantages which are particularly accentuated when the valve is heated with current derived from the electric light mains owing to the fact that the space current is not enclosed or confined by the anode. This non-confinement of space current may result in charging up of the glass walls giving interference from this cause or reaction or may render the valve highly susceptible to interference from outside sources, particularly the house wiring of the electric light supply and especially where this is brought within the valve envelope.

The invention, however, is also applicable to tubes having ordinary low voltage filaments.

According to the present invention the anode either does not surround the other electuted by a helix having relativel closely spaced turns. Furthermore, anot er electrode which is preferably also of openwork formation is disposed without the anode and is arranged to be operated at a potential lower than that of the anode, and preferably at zero potential for which purpose it may be connected to the cathode, whereby electrons are prevented from appreciably passing through theopenwork anode and the space current is shielded from interference from an external source or from the circuits coupled with the device or from the charges which would otherwise accumulate on the glass walls of the device. Such outer electrode when perforated will also allow the heat generated in the cathode to be radiated through it.

If the shield is not of openwork construction but is of sheet metal, it is preferably open at at least one side, preferably the side remote from the lead-in point of the conductors carr ing the cathode heating current. In a modi cation which may be adopted when the current for the cathode or cathode heating means is led out at one end of the electrodes, or when the conductors therefor are screened. The further electrode may, in a simplified form, consist of a plane sheet of metal or gauze or the like, extending across the device at the end of the electrodes adjacent to the point of leading out the cathode heating current, whereby the space current is screened from voltage surges or ripples in the heating current leads. This type of construction may sometimes be profitably employed when the valve is screened externally.

According to another feature of the present invention, in order to prevent or reduce interference or hum which may be picked up in or by the valve from disturbances present in the supply mains, such as commutator ripple andsurges in the case of direct current or the fundamental wave and its harmonics in the case of alternating current, the electrical conductors provided within the valve between the resistance heater or auxiliary member and main cathode on the one hand and the seal for these conductors on the other hand are provided with one or more shields or screens which are electrically connected to a conductor which is at or will be operated at a constant potential; preferably said screen or screens is or are connected to the cathode.

The invention equivalently contemplates the provision within the valve of a screened resistance connected in series with the internal leads to the. heater. or auxiliary member.

By these screens, the variations of voltage which occuriion the conductors or the series resistance due to ripples or surges in the voltage or due to the fundamental frequency and its harmonics are prevented from afiectmg the inter-electrode space current or stray space current in the vacuum electric tube device.

To enable the invention to be clearly understood, it will now be described with reference to the accompanying drawings which illustrate, by way of example, several electrode structures in accordance with the invention, which structures themselves form subsidiary features of the invention, subject to the limitations herein mentioned.

Fig. 1 is a sectional front elevation of one electrode structure, Fig. 2 is a side elevation of the structure shown in Fig. 1, and F1 3 is a sectional plan view on the line III-- II of Fig. 1.

Fi 4 is an elevation, partly in section, of a mo 'fied arrangement, and

Fig. 5 is an elevation, partly in section, of a still further arrangement.

Referring first to Figs. 1, 2 and 3 of the drawings, the electrode structure therein 11- lustrated is for a valve intended to operate from ordinary electric supply means andalso as set forth in the specification of Brit sh Patent No. 195,691, namely, wherein the inter-electrode space is small and the spaced current confined to said small inter-electrode space.

The cathode comprises a nickel tube 1 within which is disposed a carbon heater (not shown) wound on a porcelain rod 2 which is centred within the tube 1 by means of metal clips 3. The equi-potential cathode is mounted on a wire 4 secured into the pinch or seal of the valve and is connected to one of the leads of the heater or to a separate terminal, as desired. It will be understood that such cathode is mentioned by way of examle only and that other forms of cathode may he used if desired including ordinary low voltage filament cathodes such as are usually an lied b means of accumulators.

l e gri may be of any desired construction, such, for example, as the illustrated wire helix 5 secured to a pair of parallel support wires 6 held in the pinch or seal.

The anode is in the form of an openwork tube, namely of wire gauze 7 welded to two support wires 8 or it may, however, if desired, comprise alternatively a helix with comparatively closely spaced turns. Around the anode 7 is a further tube of wire gauze 9 (or alternatively a helix with closely spaced convolutions may be used) supported on a pair of wires 10 secured in the pinch or seal. The outer tube 9 is electrically connected to the cathode by means of the wire indicated at 11.

In the arrangement shown, the upper end of the cathode tube 1 is located or registered with respect to the other electrodes by means of a metalwasher 12 which is peripherally welded to the support wires 10 of the outer openwork tube 9 whilst its perforation receives the upper end of the cathode tube 1.

One of the heater leads brought out through the pinch or seal is indicated at '13, namely, from the lower end, whilst the lead from the upper endis indicated at 14 passing around outside the electrodes. The lead 14 is shielded by means of metal tubes 15, there being three such tubes in the example shown. The tubes 15 may be supported from the lead wire 14 by means of'glass tubes, beads or the like indicated at 16. The tubes 15 are electrically connected to a point of low potential, namely,

the cathode for instance, by means of wires 17 which are welded to the outer openwork tube 9 and which serve as supports for the metal tubes 15, the insulators l6 and the lead wire 14.

In the structure described, which is illustrated to an enlarged scale for the sake of clearness, the inter-electrode space between the cathode 1 and the anode 7 is small and the discharge is confined to this space by providing an oxide coating 18 on the central portion only of the tube 1. That is to say, no

emission occurs from the end portions of the tube, which portions therefore act as electrostatic screens for confining the electrons. It will be appreciated also that the washer 12 which is at the potential of the cathode acts as an additional shield for the purpose. If desired, a similar shield may be provided at the lower end of the electrodes.

In a modification of the arrangement shown in Figs. 1, 2 and 3, the outer tube 9 may cons sist of sheet metal and in this case the washer 12 is preferably replaced by a cross strip or is of openwork formation in order that the space within the tube 9 may be opened. Such opening, however, is not necessary in valves in which the cathode and anode heat dissipation is comparatively small.

Referring now to Fig. 4 of the accompany-- ing drawings, the structure therein illustrated is, in general, similar to that shown in Figs. 1, 2 and'3. A modified form of equi otential cathode 1 however, is illustrate the heater of which comprises an insulating rod 2 which fits snugly within the cathode tube and has formed in it two longitudinal holes within which are accommodated the limbs of a hairpin heater 19 of tungsten or carbon, for example. If desired, such limbs of the heater-may be in the form of helices of small exhandand said electrode structure on the ternal diameter and with closely spaced turns. other hand.

The grid and anode 7 may be similarly con- In testimony whereof, I have hereunto substituted and supported as in the arran ement scribed my name this thirtieth day of Ocshown in Fi s. 1, 2 and 3. The catho e tube tober, 1928.

1 is preferab y closed at its up r end and has ERNEST vYEOMAN ROBINSON.

a wire welded to it centra y, which wire 1 passes through a perforation in an insulating crosspiece 21 which is provided with further perforations within which are accommodated T8 the upper ends of the support wires for the grid and anode. The crossiece 21 may consist of mica, stcatite or porce sin, for example. Extending across the valve in a screen 22 in u the form of a disc supported on wires 23, se- I I cured in the pinch or seal, this disc bein provided with clearance holes through whic the support wires for the anode and id pass. It is provided with a central ole :0 within which snugly fits the cathode tube 1.

Preferably the disc 22 and the cathode tube 1 are electrically connected together by means of a wire.

The screen 22 prevents voltage surges in 25 the heater connections such as 13 and 14 from interfering with the space' current stream within the valve, and particularly the stra electrons assin throu h the 0 enwor anode. If esired, a cylin er 24 of wire gauze 30 or a helix ma be attached to the disc 22. 08

Referring astly to Fig. 5, in the structure therein illustrated, the electrodes, may be constituted, in general, similarly to those previously described. The heater leads are led 35 out from the top of the cathode and throu h v the 11 per end of the valve envelope. T e cathode leads have connected in series, a resistance 25 which convenientl consists of a carbon or tungsten wire coile into a helix 0 and supported on a spider 26 formed of a 165 pluralit of wires fused into a glass stem 27 whic in turn is fused to a pinch or seal 28 at the upper end of the valve envelope.

Wires 29 extending upwards from the a lower pinch or seal carry a shield in the form of a disc 30 which is provided. with a central perforation registering the cathode tube 1.- The wires 29 are mechanically connected with the glass stem 27 by means of wires 31 w by which arran ement the space relationship I 116 I of the two pinc es or seals may be fixed be fore the feet are sealed to the main envelope. It will be understood that various detail modifications may be made within the scope 55 of the invention. 120

I claim as my invention: A vacuum electric tube device comprising an electrode structure comprising 8.118(1111- potential cathode, an electrical heater there- 0 for, a grid, an anode having numerous openings therein to permit of substantial radiation of heat from the cathode, and a screen connected to said cathode and extending across the device between the pdint of lead- V 6! ing out the heater connection on the one 

